The present invention relates to the control of communication channels in a communication system comprising a base station and several terminals. It has a particular, non-exclusive, application in cellular networks for radio communication with mobiles.
In communication systems, it is conventional to manage the allocation of channels by way of a control facility. The latter is in fact furnished with a set of communication resources that it can distribute at its convenience, for example upon a traffic channel request by a user.
The control facility therefore makes communication channels available to a base station so that the latter can communicate with terminals under its zone of coverage. The control facility and the terminal converse according to a resource management protocol, transparent to the base station, in particular so that the terminal is informed of the channels to be used, in the form of a subset of the communication channels allocated to the base station.
Such management of the communication channels exhibits some rigidity since it necessitates systematic intervention from the control facility in case of reallocation of the communication channels, if for example one wishes to use, for a terminal, channels that have not been assigned to it specifically at the start of its communication session with a base station. Now, there are various circumstances where a reassignment of resources may seem to be desirable at the base station level without it being opportune to advise the control facility thereof, for example for reasons of management of the hardware and/or software resources within the base station or else because the delay occasioned by the exchange with the control facility is not acceptable having regard to the characteristics of the service.
In certain cases, the control facility allocates the base station a set of channels without signaling them especially to the terminal. When the base station needs to communicate with the terminal, it selects one of these channels and indicates it to the terminal, for example on one or more associated signaling channels. Such a procedure is well suited to the implementation of fast communication services over traffic channels shared between several terminals. The associated signaling channels are also shared channels. The terminal must then know the associated signaling channel or channels that it may have to listen to. If these channels are assigned to it by the control facility, the above problem arises again each time the need appears, at the base station level, to reassign the shared signaling channels used for a given terminal.
Another possibility of letting the terminal know the shared channel or channels to be used consists of a fast signaling mechanism, for example one using symbol stealing, over a dedicated communication channel set up with the terminal. However, this may result in an undesirable reduction in the bandwidth afforded by this dedicated channel, in particular if the list of possible channels is relatively extensive or unknown a priori to the terminal.
An object of the present invention is to improve the flexibility of these methods of managing shared communication channels.